In practice, diverse methods are used to liberate the antigens, namely heating to 100.degree. C., an enzymatic treatment at 37.degree. C. or an extraction with sodium nitrite in two operational steps.
Another known procedure for the extraction of these antigens is a treatment with high-percentage phenol, e.g. 90% saturated phenol (90% phenol/10% water) at a temperature of 60.degree. C.
The heating to 100.degree. C. as well as the enzymatic treatment for the antigen liberation can not be effected in the presence of specific antibodies, since these are denatured. A re-pipetting must also be effected. The same applies in the case of a high-percentage phenol extraction, which additionally requires a centrifugation. The extraction with sodium nitrite involves two separate reagents and subsequent treatment with Tris buffer.
This means that these known procedures are extremely circumstantial and time consuming and are therefore anything but conformable in practice.